Fluid oscillator



March 17 1964 Filed Feb. 1, 1963 K. E. WOODWARD 3,124,999

FLUID OSCILLATOR 2 Sheets-Sheet 1 43 I INVENTOR/ KENNETH E. WOODWARD BY m" 3% March 1964 K. E. WOODWARD FLUID OSCILLATOR 2 Sheets-Sheet 2 Filed Feb. 1, 1963 KENNETH E. WOODWARD United States Patent 3,124,999 FLUID OSCILLATOR Kenneth E. Woodward, McLean, Va., assignor to the United States of America as represented by the Secretary of the Army Filed Feb. 1, 1963, Ser. No. 256,217

5 Claims. (Cl. 91--3) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereon.

This application is a continuation in-part of my copending application serial No. 102,905 filed April 13, 1961, now abandoned, for Fluid Oscillator.

This invention relates generally to a fluid system for oscillating a piston in which the movement of the piston generates fluid pulses. These pulses ultimately determine the rate of oscillation of the piston and accordingly, the output of the system.

Prior art fluid actuated systems require the use of at least two moving elements to produce oscillation of one of the elements. The latter element is usually a piston which is slidable in a chamber and capable of actuating a suitable load device by means of a rod or similar linkage connected to the piston. The former element is usually some type of flow reversing valve which must also oscillate in order to permit alternating flow of fluid into opposite ends of the chamber housing the piston.

Such prior art systems have two main disadvantages. First, they have high time constants because of the inertia and friction of the moving valve and piston. Second, since at least two moving elements are required, these systems are not as systems which require lesser numbers of moving elements.

Recently, pure fluid oscillators have been developed. These oscillators require no moving parts to produce an oscillating out-put fluid pulse. Basically such oscillators comprise a fluid amplifier and some means for storing and feeding back to the amplifier fluid'energy in order to cause alternating deflections of the power jet of the fluid amplifier. Using pure fluid oscillators, the piston is driven directly by the oscillating output fluid pulses. The piston can be employed to produce a pulse fluid output signal. The piston can also be employed to control the entrance of a secondary fluid source to furnish control pulses to the fluid amplifier.

It is an object of this invention to utilize the oscillation of a piston driven by the output flows from a fluid amplifier to control the sonic pulses or flow to the control nozzles of the amplifier thereby governing the rate of oscillation of the amplifier.

Another object of this invention is to provide a fluid amplifier in combination with a single moving piston which can actuate a load device, and which also serves to convert the amplifier to an oscillator.

Still another object of this invention is to provide a fluid oscillator which has a pulsed fluid output signal.

A further object of this invention is to provide a fluid oscillator in which a secondary fluid source is utilized for the control signal pulses.

7 According to this invention, a piston housed in a fluid receiving chamber is driven by fluid from the output tubes of a conventional fluid amplifier. Tubes connected to the control nozzles of the amplifier are alsoconnected to ports in the chamber. These ports are alternately covered and uncovered by movement of the piston so that sonic pulses or flows from the output tubes enter the tubes connected to the control nozzles. As a result, alternating fluid pulses are received by the control nozzles and these pulses ultimately oscillate the power jet flowing through 3,124,999 Patented Mar. 17, 1964 "ice the amplifier. The frequency of oscillation depends primarily upon the spacing of the ports and the length and mass of the piston and the volumetric flow rate.

-In fluid amplifier systems of the type with which the present invention is concerned, a power jet of fluid, which is well defined in space, is deflected by means of a pres sure differential established approximately transverse to the normal direction of movement of the power jet. The differential in pressure established across the power jet may be employed to deflect the jet to one of various positions at which load devices may be situated. These devices may convert a portion of the energy of the fluid stream to useful work. Alternately, the energy, pressure or mass flow of the deflected stream may be employed as an input signal to a further fluid amplifier or a fluid amplifier system to increase the overall amplification of the system or to perform switching functions. Amplification is achieved by the fluid amplifier as a result of the fact that a relatively small control fluid flow is required to deflect a high energy fluid stream so as to produce a relatively large variation in energy, pressure or mass flow, delivered to an output location.

A typical single stage amplifier, chosen for purposes of ease of explanation only, may comprise a main fluid nozzle extending through an end wall of an interaction region defined by a sandwich type structure consisting of an upper plate and a lower plate (which serve to restrict fluid flow to an approximately two-dimensional flow pattern bet-ween the two plates), and end wall, two sidewalls (hereinafter referred to as the left and right sidewalls), and one or more dividers dispose-d at a predetermined distance from the end wall. The leading edges or surfaces of the dividers are disposed relative to the main fluid nozzle centerline so as to define separate areas in a target plane. The sidewalls of the dividers in conjunction with the interaction region sidewalls establish the receiving apertures which are entrances to the amplifier output channels. Completing the description of the apparatus, left and right control orifices may extend through the left and right sidewalls, respectively. In the complete unit, the region bounded by top and bottom plate, sidewalls, the end wall, receiving apertures, dividers, control orifices and a main fluid nozzle, is termed an interaction region or interaction chamber region. The unit described above is capable of operation as one of several subtypes of fluid amplifier units depending upon the specific arrangement of the unit.

Two broad classes of pure fluid amplifiers are: Class I, based on stream interaction or momentum exchange; and Class II, based on boundary layer control. Class I amplifiers include devices, in distinction to the devices of Class II, in which there are two or more streams which interact in such a way that one or more of these streams (control stream) deflects another stream (power stream) with little or no interaction between the side walls of the interaction region and the streams themselves. Power stream deflection in such a unit is continuously variable in accordance with control signal amplitude. Such a unit is referred to as a continuously variable amplifier or computer element. In an amplifier or computer element of this type, the detailed contours of the side walls of the interaction chamber are of secondary importance to the interacting forces between the streams themselves. Although the side walls of such units can be used to contain fluid in the interacting chamber, and thus make it possible to have the streams interact in a region at some desired ambient pressure, the side walls are so placed that they are somewhat remote from the high velocity portions of the interaction streams and the power stream does not approach or attach to the side walls. Under these conditions the power stream flow pattern within the interacting chamber depends primarily upon the size,

speed and direction of the power stream and control streams and upon the density, viscosity, compressibility and other propertiesof the'fluids in these streams. A typical Class I amplifier is disclosed in the June 1960 edition of Science and Mechanics Magazine, pages 81-84, inclusive.

The present invention also relates to the-second broad class (Class II) of fluid amplifier and computer elements; thatis, boundary layer control units. This second broad class of fluid amplifier and computer elements comprises units in which the main power stream flow and the surrounding. fluid interact in such a way with the interaction region sidewalls that the resulting flow patterns and pressure distributions within the interaction region are greatly aflcted by the details of the design of the chamber walls. i i

The'power stream deflection effect in boundary layer units is the unit of transverse pressure gradient due to a diflerence'in the eflective pressures which existbetween the power stream and the opposite interaction region sidewalls; hence, the term boundary layer control. In order to eirplain this effect, assume initially that the fluid stream is issuing from the main nozzle and is directed toward the apex of a centrally located divider. The fluid issuing from the nozzle, in passing through the chamber, entraius some of the surrounding fluid in the adjacent interaction regions and removes this fluid therefrom. If the fluid stream is slightly closer to, forinstance, the left sidewall than the right sidewall, it is moreeffective in removing thefluid in the interaction region between the stream and the left wall than it is removing fluid between the stream and the right wall since the former region is smaller. Therefore, the pressure ,in, the left interaction region between the left, sidewall and power stream is lower than the pressure in the right interaction region, and a differential pressure is set up acrossthe power jet tending to deflect it towards the left sidewall. As the stream is deflected further toward theleft sidewall it becomes even more eflicient in entraining fluid from the left interaction region and thefeflective pressure in this region is further reduced. In those units which exhibit lockon features or characteristics, this feedbackTtype action is self-reinforcing and results in the fluid power stream being deflected toward the left wall and predominantly entering the left receiving aperture and outlet channel. The stream attaches to and is then directly deflected by the left sidewall as the power stream effectively intersects the left sidewall at a predeterminedv distance downstream from the outlet 'of the main orifice, this location being normally referred to as. the attachment location. This phenomenon is referred to as boundary layer lockon. Theoperation of this type of apparatusmay be completely symmetrical in that if the stream had initially been slightly deflectedtoward the right sidewall rather than the left sidewall, boundary layer lock -on would have occurred against the right sidewall.

Control of these units can be effected by controlled flow of fluid into the boundary layer region from control orifices at such a rate that, the pressure in the. associated boundary layer region becomes greater than the pressure in the opposing boundary layer region located on the opposi'e side of the power stream and as a result the stream is switched towards this opposite side of the unit.

The control flow maybe atsuch a rate and volume as to deflect the power stream partially byrnomentum interchange so thata combination of the two effects may be employed, However, it is not essential, and in many cases is undesirable, thatv the control flow have a momentum component transverse to the power stream when the control fluid issuesfrom its control orifice.

In both classes of amplifiers only a small amount of energy is requiredin the control signal fluid flow to alter thefpow er jet path so that some or all of the power jet becomes intercepted by the load device or output channel. For a continuously applied control signal, the power gain of this system can be considered equal to the ratio of the change of power delivered by the amplifier to its output channel or load to the change of control signal power required to effect this associated change of power delivered to the output channel or load. Similarly, the pressure gain can be considered equal to the ratioof the change of output pressure to the change of control signal pressure required to cause the change, and the mass flow rate gain can be defined as the ratio of the change of output channel mass flow rate to the associated change of control signal mass flow rate.

In the discussion a two dimensional configuration has been described for purposes of clarity. However, the invention and description relative thereto are also inclusive of configurations which are three dimensional in nature, as for example, axially symmetric units which result from rotation of a plan view about an axis coincident with the power nozzle centerline.

The specific nature of-the invention, aswell as other objects, uses, and advantages thereof, will clearly appear from the following description and from the accompanying drawings in which FIGURE 1 is a plan view of an embodiment of the fluid oscillator constructed in accordance with this invention.

FIGURE 2 is a. plan view of a second embodiment of this invention.

Referring now to FIG. 1, there isshown a fluid amplifier 10. Amplifier 10 is a Class II type amplifier discussed above,and althoughit will be evident that a, Class I amplifier may also be used, I have found it preferable to employ the former type of amplifier. Amplifier 10 is formed by three, flat plates 11, 12, and 13. Plate. 12 is positioned between plates 11 and 13 andistightly. sealed between theseplates by. anadhesive or, other suitable means such as machine screws 14. Plates 11, Hand 13 maybe composed of any suitable material such as metal, ceramic or plastic. Also, for purposesof illustration the plates are shown composed of a transparentplastic material such as lucite. Plates 11 and. 13 preventspreading of the powerand control streamsreceived by amplifier 10 in a direction normal to the deflecting plane.

The substantialy Y-shaped configuration cut or etched from plate 12 provides a power nozzle 15, control nozzles 16 and 17, fluid receiving channels 18 and 1 9, fluid bleeding channel 20, and an interaction chamber 21. Nozzles 15 and 16 are adjacent to each other and are at substan tially right angles. Controlnozzle 17 is positioned opposite nozzle 16. Channel'Ztl bleeds ofi" chamber 21 so that pressures developed in chamber 21 will be limited.

Output tubes 25 and 26 are threadedly connected to the ends of channels 18and 19 -and receive fluid therefrom. Tube 27' is threadedly connected to power nozzle 15 while tubes .28 and 29 are each threadedly connected at ends 28a and 29a to control nozzles 16; and 17, respectively. The, connections between the tubes and the nozzles aswell as the tube connections to the channels should be. made tight enough to prevent leakage.

A source of pressurized fluid (not shown) may be C011! nected to. tube 27. The source of fluid may be air, gas, water or other liquids, The. gas or liquid may have small solid particles or bubbles entrained therein. If necessary, a fluid regulating valve (not shown) may. be used to regulate the amount of fluid entering tube 27.

When fluid under pressure isapplied to the power nozzle 15, there is flow through the power nozzle. which resultsin the creaction of a power jet. Initially the power jet passes through chamber 21 substantially undeflected. As a result of viscous interaction between the power jet fluid and the surroundingfluid, the surrounding fluid is accelerated in the power jet direction as a result of momentum exchange. The entrainment of the fluid surrounding the, stream transports the fluid on each. side of the power jet out ofchamber 2 1. The action lowers the pressure on each side of the power jet. and counterflow' fluid flowing down and from channe1'20 enters chamber 21 to replace the fluid entrained and removed by the power jet.

The power stream flow through chamber 21 creates a turbulence in the chamber and therefore differential pressure perturbations will exist transverse to the power jet. The pressure perturbations deflect the power jet slightly to an asymmetric flow configuration. The effect becomes asymmetrical to a degree which increases with increasing sidewall length.

Assume for purposes of discussion that because of perturbations in flow, deflection is towards sidewall 22. This deflection reduces the area between power stream and sidewall 22 and reduces the pressure in the right boundary region, defined by right sidewall 22, the interaction chamber end wall 24, and the power stream, which region is being evacuated by the power stream entrainment.

As the gap between sidewall 22 and the power stream is further reduced, the net flow to the right boundary layer is further modified. This modification results in decrease of the right side effective pressure while the left boundary region effective pressure tends to increase towards the ambient fluid pressure level in chamber 21. The resulting transverse force inclines the power stream toward wall 22. When the sidewalls 22 or 23 are sufficiently close to the leading edges of the dividers 120 and 121, the cumulative action results in the power stream contacting wall 22 at an attachment location. When this happens the power stream establishes a sealed boundary region along the sidewall 22, causing the power stream to completely lock-in to wall 22 and flow out channel 18 and tube 25.

Should control nozzle 16 issue fluid into the boundary layer, the pressure in the boundary layer will increase until there is no tendency for the stream to remain locked-on to wall 23. Fluid will then issue from output tube 26.

It will be obvious that jets issuing from control nozzles 16 and 17 in an alternating manner will cause oscillation of the power jet between tubes 25 and 26.

Numeral 31 refers generally to the above-referred to valve system. System 31 comprises a hollow cylinder 32 in which piston 33 reciprocates.

Tube ends 25a and 26a are threadedly connected to ports 34 and 35 communicating with cylinder 32. System 31' is of the double acting type wherein the pressure is applied alternately to the chambers formed by the opposed heads 36 and 37 of the piston and cylinder 32. Another pair of ports 33 and 3*) are formed in the chamber walls and are threadedly connected to the tube ends 28a and 29a. These ports are located substantially intermediate the length of the cylinder as shown and are spaced apart a predetermined distance. As can be seen from FIG. 1, when fluid flow from tube 25 drives the piston a distance sufficient to uncover port 38 fluid will travel as flow or as a sonic pulse into this port, into tube 23, and finally into the control nozzle 16. Fluid issuing from the control nozzle will deflect the power jet in amplifier into tube 26 from whence it will drive piston 33 towards the right (as viewed in FIG. 1), uncovering port 39 and permitting some of this fluid to enter tube 29. Fluid entering tube 2% also issues as a jet from control nozzle 17 which deflects the power jet in amplifier 10 from tube 26 to tube 25. The described cycle thereafter continues and the rate of oscillation of piston 33 will depend upon the length and mass of the piston, the volumetric flow rate, and the spacing between the ports, as will be apparent to those skilled in the art. The relative lengths of cylinder 32 and piston 33 should be such that fluid is issuing from either tube end 25b or 2612 as the piston approaches that end of the cylinder. The piston Will thereby be cushioned by fluid at all times during reciprocation.

Channel 25 is connected to a control bleeder tube, referred to by numeral 35. The inside diameter or" this tube determines the loading character of the amplifier, as will be evident to those skilled in the art. The fluid 6 bled off by tube 30 can be fed back into the sump (not shown) which supplies fluid to the power jet, or can be fed into the atmosphere as shown in FIG. 1.

Piston 33 provides the only moving element in my system and performs the dual function of providing a reciprocating movement and governing the frequency of oscillation of the system. When the piston is increased in length, the frequency of oscillation decreases. Decreasing the piston length increases the frequency of oscillation. The frequency of oscillation can also be varied by varying the distance between ports 38 and 39. Increasing the distance between the ports decreases the rate of oscillation, while decreasing the distance between ports increases the rate.

The reciprocation of piston 33 can be-utilized to drive a rod linkage or the like, or the piston may drive another member so as to produce a pulsed output to a continuous high pressure stream of fluid. The last mentioned function may be achieved by providing a second cylinder 40, coaxial to cylinder 32. Piston 41 having sections 41a and 41b and an annular groove 42 therebetween reciprocates in cylinder 40 as a result of being connected to the cylinder by rod 43. A pair of opposed tubes 44 and 45 communicate with cylinder 32 by means of parts 46 and 47. Tubes 44 and 45 are designed to convey streams of fluid at high pressure. Flow between tubes 44 and 45 occurs when groove 42 is opposite ports 46 and 47 and ceases when sections 41a and 4115 block these ports. By varying the rate of oscillation of piston 41 or by varying the length of groove 42 and the piston sections, continuous flow through one tube 44 or 45 may be converted to a pulsed output flow from the other tube at any desired frequency.

FIG. 2 illustrates a system in which the piston controls the flow of fluid at high pressure from an external source to the control nozzles of amplifier 10 in order to effect oscillation of the piston. As shown in that figure, system 50 comprises a cylinder 51 in which piston 52 reciprocates. The piston can be alternately driven by fluid issuing into the ends of chamber 51 by flow from tubes 25 and 26.

Piston 52 is divided into two sections 52a and 52b by annular groove 53. Ports 54, 55, 56 and 57 are, respectively, positioned opposite each other and provide communication between tubes 58 and 59 and tubes 28 and 29. Tubes 58 and 59 join at T-junction 60. These tubes are designed to receive fluid at high pressure from any conventional source (not shown).

When groove 53 is opposite ports 56 and 57, as shown in FIG. 2, tube 59 will supply fluid to tube 29 and to control nozzle 16, causing the power jet from nozzle 15 to issue from tube 26. Fluid issuing from tube 26 drives piston 52 until section 52a no longer blocks ports 54 and 55. At that time, section 52b will move to a position where it blocks ports 56 and 57 so that fluid no longer flows to control nozzle 16, but rather flows through tube 58, port 54, piston slot 53, port 55, tube 28 to nozzle 17 deflecting the power jet from nozzle 15 into tube 25. Fluid from tube 25 drives piston 52 to the left, as viewed in FIG. 2, until groove 53 is again opposite ports 56 and 57, at which time ports 54 and 55 will be blocked and fluid from tube 59 will again flow into nozzle 16. The pulsing of fluid through T-junction 60 can be employed as a source of timed pulse signals by means (not shown) intermediate the source and the T, or in one of the control tubes 28 or 29.

As is the case with the system disclosed and shown in FIG. 1, for any fluid pressure level the rate of oscillation of the piston will depend upon the spacing of the ports, the length and position of the groove in the piston as well as the piston mass.

As will be apparent to those in the art, windshield wipers and other types of devices which are required to perform oscillating or reciprocating functions may be connected to and driven by the piston, or the piston may be employed to valve hot or cold gases or liquids under high pressure, or to, deliver enact amounts of fluids to be canned, such as beer.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in structure and arrangement within the scope of the invention as defined in the appendedclaims.

I claim as my invention:

1. In a fluid oscillator;

(a) a fluid power source; 7

(b) a fluid amplifier comprising a power nozzle connected to said fluid power source,

(c) said power nozzle issuing a power jet,

(d) a pair of opposed control nozzles positioned to direct fluid jets against said power jet in such a manner as to cause amplifier displacement of said power j (e) a pair ofopposed output tubes positioned to receive said power jet as a result of displacement by fluid issuing trom said control nozzles; and

(f) oscillating means adapted toperiodically direct fluid flow into a predetermined combination of ports termed in saidoscillating means,

() said control nozzles and output tubescommunicatingwith said oscillating means by means of said ports,-

(h) said ports being arranged such that fluid issuing from one output tube is directed by said oscillating means into that control nozzle whichis positioned to deflect said power jet into the output tube opposite the tube issuing fluid.

2. In a fluid oscillator as recited in claim 1, said oscillatingmeansinoludinga piston having two ends. wherein said ends direct said power jet into the proper control nozzle when proper-ly,positioned.

3. in a fluid oscillator as recited in claim 1,

(a) said oscillating means includinga piston having a central channel therein,

(b) said power source connected to two oi said ports in said oscillating means and said ports which communicate with said control nozzles being alternately connected to one of said vpower sourceports when the central channel of said piston is properly positioned. 1

4. In a pulse generator,

(a), a fluid power source for producing a fluid power stream,

(b) a fluid amplifier having wall lock-on characteristics,

(c) an oscillatory. body means having an oscillatory body. therein,

(d) first conduit means connecting said fluid power source to said fluid amplifier,

1(e) second and third conduit means connecting said I fluid amplifier, to said oscillatory body means for providing fluid power thereto,

(f) fourth and fiithconduit meansconnecting said oscillatory body means to said fluid amplifier for providing control signals to said fluid amplifier (for selection of directing the power stream trom said fluid 8 power source into one of said second and third conduit means.

5. In a pulse generator;

(a) a fluid power source for issuing a power stream;

(12) a fluid amplifier having wall lock-on characteristics including a power nozzle means,

(0) a right and a left control nozzle means,

(d) and a right and a left receiver means;

(e) an oscillatory body means including a piston means,

(f) means for confining the movement of said piston means to a single plane,

(g) and first, a second, a third and a fourth port means in said means for confining said movement;

(It) first conduit means connecting said fluid power source and said power nozzle means,

(1') second conduit means connecting said left control nozzle means to said second port,

-( j) third conduit means connecting said left receiver means to said first port,

(/c) fourth conduit means connecting said right receiver means to said fourth port,

(1) fltth conduit means connecting said right control nozzle means to said third port,

(m) said tour ports being positioned to provide said power stream to move said piston with said first and fourth ports being positioned beyond the limits of travel of the ends of the piston,

(11) and said second and third ports being positioned intermediate said first and fourth ports so that said third port is uncovered by said piston \when said piston is at its limit of travel near said first port and said second port is uncovered by said piston when said piston is at its tlimit of travel near said fourth port,

whereby application of said power stream through said power nozzle, said left receiver means, said third conduit means and said first port will force said piston toward said fourth port until said second port is uncovered and said power stream is then directed through said second port,

said second conduit means and said left control nozzle to redirect said power stream irom said tleft receiver means to said right receiver means and through said fourth conduit means,

said fourth port to return said piston toward said first port until'said third port is uncovered and said pow-er stream is then applied throughsaid third port,

said fifth conduit means and said right control nozzle to return said power stream from said right receiver means to said left receiver means.

References Cited in the file of this patent UNITED STATES PATENTS 632,931 Weinman Sept. 12, 1899 1,826,363 Miedbrodt Oct. 6, 1931 2,240,163 Pick Apr. 29, 1941 3,004,547 Hurvit-z Oct. 17, 1961 3,016,066 Warren Jan. 9, 1962 

1. IN A FLUID OSCILLATOR; (A) A FLUID AMPLIFIER COMPRISING A POWER NOZZLE CON(B) A FLUID AMPLIFIER COMPRISING A POWER NOZZLE CONNECTED TO SAID FLUID POWER SOURCE, (C) SAID POWER NOZZLE ISSUING A POWER JET, (D) A PAIR OF OPPOSED CONTROL NOZZLES POSITIONED TO DIRECT FLUID JETS AGAINST SAID POWER JET IN SUCH A MANNER AS TO CAUSE AMPLIFIER DISPLACEMENT OF SAID POWER JET, (E) A PAIR OF OPPOSED OUTPUT TUBES POSITIONED TO RECEIVE SAID POWER JET AS A RESULT OF DISPLACEMENT BY FLUID ISSUING FROM SAID CONTROL NOZZLES; AND (F) OSCILLATING MEANS ADAPTED TO PERIODICALLY DIRECT FLUID FLOW INTO A PREDETERMINED COMBINATION OF PORTS FORMED IN SAID OSCILLATING MEANS, (G) SAID CONTROL NOZZLES AND OUTPUT TUBES COMMUNICATING WITH SAID OSCILLATING MEANS BY MEANS OF SAID PORTS, 